I know this might seem like a weird idea to some of you, since nails aren't an all important part of cosplay. But, to me, they are.
You seem I often end up doing characters who sport their nails as claws (Sesshomaru, Oodana, etc). So I file them each week in a point and sport that look all year round. It's my simple, delicate, cosplay touch in my boring everyday life.
Thing is, con-crunch tends to make you go super fast, be less delicate, or plain old clumsy (I'm looking at you guys, using your dremmel on that last piece of armor at 1am the day before the con). Now you've got a rip, in that perfect claw you'v been growing for the past month and it'll likely cut off so short it'll be a pain for a week and your cosplay detail is ruined.
Keep calm and breathe. You can fix that(as long as it's still at least slightly holding in place).
Fixing a torn up nail
Transparent nail polish
Nail polish the color of your choice
Additional but not necessary materials :
Cut a small piece of the tea bag that fits over the rip in your nail.
Put one layer of transparent nail polish on your nail and immediately place the small teabag cutout on the rip
Cover with another layer of transparent nail polish before the first coat is set so it get embedded in it.
To be ultra sure and secure, repeat steps 1 to 4.
If you have a nail buffer block, it is now time to use it to slightly smooth-out the patch you've made.
Add smooth-on base-coat on all your nails to start working on your cosplay look.
Once dry, apply the color of nail polish of your choice
Finish with a top-coat
People will now wonder how the heck you managed to keep your nails long and pretty without using acrylic nails for your cosplay, and you won't have to end up with an overly sensitive finger once you're back at work. Win-win.
Different nail looks I've sported for Yokai cosplays:
Sesshomaru : Pure white nail polish and matte top-coat (very intense looking claws)
Kokkuri-san : Pure white nail tips and glossy top coat (meant to be cute and softer claws)
Oodanna : Black and matte top-coat